The present invention relates to a magnetic head, and a magnetic recording and playback drive comprising the same.
A magnetic head for use in a magnetic recording and playback drive has a magnetic recording head and a magnetic read head (magnetic read element) which generally comprises a pair of upper and lower magnetic shields, a magnetoresistive film interposed between the shields and a pair of electric leads electrically connected to the magnetoresistive film. In the case of a magnetic recording and playback drive having an areal recording density of more than 100 G bits per inch2, a high sensitivity read element such as a giant magnetoresistive film (GMR film) or tunneling magnetoresistive film (TMR film) is used as the magnetoresistive film. These magnetoresistive films have a ferromagnetic free layer, an intermediate layer, and a ferromagnetic pinned layer; the magnetization of the ferromagnetic free layer turns according to a change in a leakage magnetic field from a magnetic recording medium in which information is recorded. Meanwhile, the direction of the magnetic moment of the ferromagnetic pinned layer is substantially fixed. When a sensing current is applied to these magnetoresistive films, the voltage of the element changes according to the angle between the magnetization of the ferromagnetic free layer and the magnetization of the ferromagnetic pinned layer, and is observed as a read waveform. A conductor is used as the intermediate layer of the GMR film whereas a barrier layer made of an oxidized material is used as the intermediate layer of the TMR film. Although the TMR film has higher element resistance than the GMR film, it has a very large read amplitude which is considered as advantageous in increasing the recording density of a magnetic recording and playback drive.
In the case of the GMR film, a sensing current is applied in the track width direction within the film plane. This type of element is generally called “CIP (current in the plane).” In the CIP element, an insulator is interposed between the upper and lower magnetic shields and the electric leads or GMR film to ensure read output. However, when the interval between the upper and lower magnetic shields is narrowed to increase the recording density of a future magnetic recording and playback drive, the above insulator becomes thin and insulation between the electric leads and the upper and lower magnetic shields deteriorates. As a result, read output greatly decreases and noise increases, thereby significantly reducing the yield of the magnetic head. As a solution to these problems, CPP (current perpendicular to the plane) in which a sensing current is applied perpendicular to the film plane is attracting attention. Since a pair of electric leads can serve as upper and lower magnetic shields in a CIP element, it is not necessary to take insulation between them into account. It is reported that the magnetoresistive ratio of the CPP-GMR film can be made higher than that of a CIP-GMR film. Meanwhile, a TMR element must be of a CPP type because it exhibits a magnetoresistive effect theoretically and a pair of electric leads can serve as upper and lower shields. The CPP-GMR film and the TMR film are thus considered as the most promising for the next-generation high-sensitivity magnetic recording head.
The magnetic read head has a domain control layer to provide a mono-domain structure to the ferromagnetic free layer. This is aimed to maintain the mono-domain structure and prevent the malfunctioning of the recording and playback drive even when the magnetic domain of the ferromagnetic free layer is magnetically influenced by the write head or the upper and lower magnetic shields. As the domain control structure is generally used a structure in which a pair of permanent magnets are arranged at both ends in the track width direction of the magnetoresistive film (JP-A 125311/1991). In this structure, the magnetic domain of the ferromagnetic free layer maintains the mono-domain structure by a magnetic field generated by the permanent magnets. For the TMR film and the CPP-GMR film, a structure that the domain control layer is formed on the ferromagnetic free layer is proposed. As the domain control layer, there is known a multi-layered film consisting of a permanent magnet (JP-A 259824/1999) or antiferromagnetic film and a ferromagnetic film.
To increase the density of a magnetic recording and playback drive, the width of each recording bit must be reduced. To attain this, (1) the interval between the upper and lower magnetic shields of the magnetic read head and the width of the read track must be reduced. At the same time, (2) the magnetic spacing which is the distance between the magnetoresistive film and the surface of the recording medium must be reduced. This is because the media fields from the recording bits are overlapped with one another when the magnetic spacing is large, thereby making it difficult to read recorded information accurately. To realize (1), the interval between electric leads and the width in the track width direction of the magnetoresistive film are reduced. To realize (2), the flying height of the magnetic head is reduced and the protective film of the recording medium is reduced in thickness.